The human parasite, Schistosoma mansoni, is a major health hazard in many regions of the world. The adult worm of this species produces a thiol-dependent, acidic protease which may be involved in the inhibition of the worm, by digesting host hemoglobin. This protease will be isolated and purified. The physical-chemical parameters of the enzyme, and its specificity will be investigated, with the aim of obtaining specific inhibitors of this protease. The inhibitors will be tested for their effect on the viability of the parasite, using in vitro culture of the worms. Specific antisera will be prepared against the enzyme in order to test for the presence of enzyme in the sera of infected animals. Quantitative immunological techniques will be utilized to determine if this enzyme is useful in the serodiagnosis of this disease.